docs: def com_google_fonts_check_whitespace_ink(ttFont):
    """Whitespace glyphs have ink?"""
    from fontbakery.utils import get_glyph_name, glyph_has_ink
  
    # code-points for all "whitespace" chars:
    WHITESPACE_CHARACTERS = [
        0x0009, 0x000A, 0x000B, 0x000C, 0x000D, 0x0020, 0x0085, 0x00A0, 0x1680,
        0x2000, 0x2001, 0x2002, 0x2003, 0x2004, 0x2005, 0x2006, 0x2007, 0x2008,
        0x2009, 0x200A, 0x2028, 0x2029, 0x202F, 0x205F, 0x3000, 0x180E, 0x200B,
        0x2060, 0xFEFF
    ]
    failed = False
    for codepoint in WHITESPACE_CHARACTERS:
      g = get_glyph_name(ttFont, codepoint)
      if g is not None and glyph_has_ink(ttFont, g):
        failed = True
        yield FAIL, ("Glyph \"{}\" has ink."
                     " It needs to be replaced by"
                     " an empty glyph.").format(g)
    if not failed:
      yield PASS, "There is no whitespace glyph with ink."